Bone and cartilage transplantation is an absolute need in reconstruction of bone and cartilage segments in plastic surgery, traumatic surgery or after the removal of neoplastic lesions, etc. Typically, material of human (autologous, from donors or from cadavers) or animal origin has been used for this purpose. Given the increased demand from clinicians for transplant tissues, the increased need for microbial safety in tissue transplantation, the advances in cell biology, cell differentiation and tissue engineering, the concept of rebuilding tissues from autologous or allogeneic cells expanded in vitro has become a growing field in the world of biomedical sciences. Cellular sources for skeletal repair include chondrocytes and cells committed to the chondrocyte lineage, and mesenchymal stem cells, the former specific for cartilage, the latter multipotential and therefore having the potential to be used to replace bone, cartilage and other tissues.
Mesenchymal stem cells (MSCs) are found in bone marrow as well as in blood, dermis and periosteum. Although these cells are normally present at very low frequencies in bone marrow these cells can be isolated purified and culturally expanded, for example, as described in U.S. Pat. No. 5,486,359.
Typically, the in vitro expansion of chondrocytes and MSCs takes place in culture medium supplemented with bovine serum or optimally with autologous serum from the patient. However, the presence of animal or autologous serum in chondrocyte and MSC cultures has certain disadvantages and limitations in view of the potential therapeutical applications of these cultures.
For example, serum is not the physiological fluid most cells closely contact in tissue in vivo. This is particularly true for chondrocytes that, in vivo, are embedded in their avascularized matrix and rely for their own growth and differentiation on various growth factors and cytokines acting in an autocrine/panacrine manner rather than diffusing from the distant bloodstream. Further, there is often high variability between animal serum batches. Extensive serum screening required to select the batch most representative of the in vivo inductive effects can be time-consuming and expensive The preparation of autologous serum from patients is also time consuming and supplies are limited. Animal serum can further potentially carry unknown pathogens with consequent risk of contamination for the patient.
Thus, serum substitutes for culturing cells for potential in vivo therapeutic applications is desirable.